Radio frequency rotary switch



Oct. 30, 1956 WALTERS 2,769,144

RADIO FREQUENCY ROTARY SWITCH Filed Jan. 11, 1952 S'dFYIMd INVENTOR.

emu/v2 M00595 P1519. 22 By find/49;

Patented Oct. 30, 1956 2,769,144 RADIO FREQUENCY ROTARY SWITCH Glenn A. Walters, Palo Alto, Calif., assignor to Dalmo Victor Company, San Carlos, C a corporation of California Application January 11, 1952, Serial No. 266,012 6 Claims. 01. 333-7 This invention relates to a radio frequency rotary switch and particularly to a high power radio frequency rotary switch.

A primary object of the present invention is to provide new and useful improvements in radio frequency rotary tron at equally spaced points thereabouts and adapted to output sections.

Another object of the present invention is to provide a rotary switch as described in the immediately-above paragraph in which the impedance mismatch naturally occurring during switchover or crossover is reduced by twisting the output sections substantially 90 degrees so, that the narrow dimension of the output end of each output section is parallel to the plane of rotation of the frequency energy assuming a non-circularly symmetrical mode.

A still further object of the provide means as described in ergy.

Various other objects will be apparent from the following description taken in connection with the accompanying drawings wherein: 1

Figure 1 is a vertical longitudinal section through a rotary switch embodying the concepts of the present invention;

present invention.

Theiparticular embodiment of the invention disclosed in the drawings includes two rectangular output waveguide sections. This particular disclosure is not intendedto limit the invention as the number of output sections may obviously'be increased as desired.

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, the rotary switch, disclosed in the figures and embodying the concepts of the present invention, comprises a fixed rectangular input waveguide section 9 joined right: angularly to a relatively short fixed circular waveguide section 11. The rotary switch is supported in a manner not shown by a support secured to these fixed parts. At the juncture between sections 9 and 11 there is formed June 29, 1951.

Coaxial with fixed circular section 11 is a;rotary circular waveguide section 15 mounted for rotary movement with respect to fixed circular section 11 by a hearing 17 fitting over circular section 15 and within a hub 19 formed on fixed circular section 11. A labyrinth radio frequency choke 21 is formed between the adjacent ends of circular sections 11 and 15 to prevent radio frequency energy at this point.

At its opposite end, rotary circular section 15 is closed by an integral cap 15a. Joined right-angularly to rotary circular section 15 are two diametrically opposed recand 25, spaced from the adjacent closed end of circular section 15 a distance chosen to be equal to one-half the wave length suming the dominant non-symmetrical mode. ingly, an impedance match between the output sections 23 and 25 and circular section 15 is achieved, and at the a same time the dominant non-symmetrical mode is supi the axis of circular section pressed.

As is apparent from Figures 1 and 2, the inner ends of rectangular output sections 23 and 25 are arranged so that their narrow or dimensions are parallel to 15 as is necessary for the 3 proper transmission of radio frequency energy from a circular to a rectangular waveguide section.

Output sections 23 and 25 are twisted approximately 90?, for purposes to be set out hereinafter, so that their outer ends have their narrow or E dimensions disposed in the plane of rotation of output sections 23 and 25, Which plane is obviously disposed at right angles to the axis of circular section 15. Standard radio frequency chokes 2 6 are fixed to the outer end of output sections 23 and'25 to prevent leakage of radio frequency energy at these points.

Disposed in registry with the outer ends of output sections 23 and 25 and movable in unison therewith are rectangular external waveguide sections 27 and 29 joined right-angularly to a rotary sleeve 31. Rotarysleeve 31 is 'rotatably supported from fixed circular section'l'l by a bearing 33 fitting within a bearing spacer 35 which in turn fits within the righthand end of sleeve 31, as the parts are depicted in Figure 1 bearing 33 fitting onto a relatively thick flange 11a formed on fixed circular section 11. A hearing retainer '37 is secured to the righthand end of sleeve 31 and against the outer race of bearing 33 by screws 39. The lefthand end of sleeve 31 is secured by screws 41 to'an end plate 43, which is formed with an annular flange 43a fitting over end cap 15'a to center'the righthand ends of sleeve 31 andsection 15'relative to one another. End plate 43 is secured to cap 151; by screws 45.

Rotary sleeve 31 and therefore external waveguide sections 27 and 29 are adapted to be rotatably driven by a drive "(not shown), rotary sleeve 31 and circular section IS 'being connected together, moving in unison to maintain the registry of the outer ends of output sections 23'and 25 'and the inner ends of external sections 27 and 29, respectively.

Disposed within rotary sleeve 31 and surrounding circular section 15 and output sections 23 and 25 is a fixed sleeve 47 secured at its righthand end, as the parts are depicted in Figure l, to flange 11a of fixed circular section 11 by screws 49. The lefthand end of fixed sleeve 47 is of reduced wall-thickness and is enlarged to provide a thin shell in which a window 47a is formed. Window47a is disposed to register with the path of travel of the outer ends of output sections 23 and 25 and extends arcuately a distance of 180 degrees as is clearly shown in Figure 2. p

Dry load elements 51, such for example as graphite wedgesnare secured to the interior of sleeve 47 'at the ends of window 47a.

' Figure 3 illustrates only diagrammatically a possible application of the rotary switch of the present invention. In Figure 3 there is shown a back-to-back reflector arrangementincluding two dishes or re'fiectors 53 and 55 suitably connected to the rotary switch by external waveguide sections 27 and 29, said rotary switch being moluntedjwithin a radar dome 57 mounted on the forward portion'of an airplane. In such an arrangement, winddow 47a of' the rotary switch is arranged to face forwardly 'asthe parts are depicted in Figure 3, that is, in a'direction tothelefnso that each dish is supplied with radiof'requency energy during movement thereof through the frontlsdde'grees of its movement, but cut off during the rear 180'degrees'of its movement, thereby eliminating the'unwanted reflection which would otherwise result when the reflector is directed toward the plane itself. With this construction, the necessity of blanking the magnetron during direction of the reflectors toward the plane is eliminated.

The rotary switch of the present invention functions as'followst Almost all theradio frequency energyentering short circular section 11 from input section 9 is converted by step 13 from a linearly polarized mode (such as the TEiq mode) into a circularly symmetrical mode (such as'the TMoi mode), and a small percentage of theinput radio frequency energy is unavoidably con-.

the TEn mode).

verted into a non-circularly symmetrical mode (such as The provision of the specially dimensioned blind portion of circular section 15 extending beyond output sections 23 and 25 presents a high impedance to the non-circularly symmetrical mode and a low impedance to the circularly symmetrical mode so that while the latter mode readily passes into output sections 23 and 25, the former mode is suppressed.

As the output ends of output sections 23 and 25 rotate, each output end is alter'nate'ly'exposed by Window 4711 of fixed sleeve 47 and then shorted by the body por tion of the fixed sleeve. As crossover, each output end is partially covered or maskedby the inner margins of fixed sleeve 47 defining the ends of window 47a. At such time these margins do not perform their shorting function as they would were they in positions to fully cover the output ends. To prevent unwanted reflection from these margins, dry load elements 51 attached thereto function to absorb the radio frequency energy directed thereagainst. Since output sections 23 and 25 are twisted degrees, the crossover period is reduced because it is the narrow dimensions across which the above-mentioned margins'relatively pass. This twisted construction also has a second advantage and that is continued transmissionthroug h the uncovered portions of the output ends of output sections 23 and 25 (since the critical E dimensions of the output ends are not reduced by the masking or covering of said ends). Ideally, since the dry load elements absorb the radio frequency energy directed thereag'ainst, and the uncovered portions of the output ends of output sections 23 and 25 continue to properly transmit radio frequency energy, there is no variation in the voltage standing wave ratio during crossover. Practically, however, the dry load elements do not function perfectly and along with other practical imperfections there results a slight but not serious difference inthe standing wave ratio during crossover as compared to that during non-crossover periods. The rotary switch, however, does have a low standing wave ratio and consequently a constant impedance.

This constant impedance makes the rotary switch acceptable from the standpoint of economical use of the generated radio frequency energy, and the substantially constant characteristic of the impedance makes the switch acceptable for use with high frequency generating devices which are affected detrimentally by variations in the'load in a manner well known to those skilled in the art.

For ease of manufacture or where minimum crossover angle is of greatest importance, the length of the rectangular waveguide from the circular guide out to the shorting plate or fixed sleeve 47 can be increased in approximately half wave length steps.

Although sleeve 47 has been shown and described as being .fixed,ji t is contemplated that the sleeve may be orientab'le. This would allow it to be incorporated in an antenna which has yaw stabilization such that the direction of the 'scanned sector may be varied at will, or varied under gyro control relative to the center line of the fixed. antenna base in azimuth.

While I have shown the preferred form of my invention, it is to be understood that various changes may be made in its construction by those skilled in the art without departing from the spirit of the invention as defined in the appended claims. I

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. 'A radio frequency rotary switch, comprising a rotarycircular waveguide member, means for feeding radio frequency energy to said circular waveguide member, a pair of diametrically opposed rectangular output waveguide sections joined to the circular waveguide member at'right'angles with respect thereto and disposedso that the narrow dimension of the inner end of each output section 'isperpendicular to the plane ofrotation "'of'the:

ouput sections, said output sections being twisted intermediate their ends to an extent such that their output ends are disposed with the narrow dimension of each parallel to the plane of rotation of the output sections, a fixed sleeve enclosing the output ends of the output sections and having a window therein in registry with the path of travel of said output ends and extending arcu- 'ately 180 degrees, and a rotary sleeve enclosing the fixed sleeve and movable in unison with the rotary part of said circular member and having a pair of diametrically opposed rectangular external waveguide sections disposed in registry with the output ends of the output waveguide sections.

2. A radio frequency rotary switch, comprising a rotary circular waveguide member, means for feeding radio frequency energy to said circular waveguide member, a pair of diametrically opposed rectangular output waveguide sections joined to the circular waveguide member at right angles with respect thereto and disposed so that the narrow dimension of the inner end of each output section is perpendicular to the plane of rotation of the output sections, said output sections being twisted intermediate their ends to an extent such that their output ends are disposed with the narrow dimension of each parallel to the plane of rotation of the output sections, a fixed sleeve enclosing the output ends of the output sections and having a window therein in registry with the path of travel of said output ends and extending arcuately 180 degrees, the margins of said fixed sleeve defining the ends of the window having dry load elements secured thereto to lessen the reflection of radio frequency energy from said margins, and a rotary sleeve enclosing the fixed sleeve and movable in unison with the rotary part of said circular member and having a pair of diametrically opposed rectangular external waveguide sections disposed in registry with the output ends of said output waveguide sections.

3. A radio frequency rotary switch, comprising a circular waveguide member having a fixed part and a rotary part, a fixed rectangular input waveguide section joined to the fixed part of said circular member at right angles with respect thereto, a pair of diametrically opposed rectangular output waveguide sections joined to the rotary part of the circular member at right angles with respect thereto and disposed so that the narrow dimension of the inner end of each is perpendicular to the plane of rotation of the output sections, said output sections being twisted intermediate their ends to an extent such that the output ends of the output sections are disposed with the narrow dimension of each parallel to the plane of rotation of the output sections, a fixed sleeve enclosing the output ends of the output sections and having a window therein in registry with the path of travel of said output ends extending arcuately 180 degrees, and a rotary sleeve enclosing the fixed sleeve and movable in unison with the rotary part of said circular member and having a pair of diametrically opposed rectangular external waveguide sections disposed in registry with the output ends of the output waveguide sections.

4. A radio frequency rotary switch, comprising a circular waveguide member having a fixed part and a rotary part, a fixed rectangular input waveguide section joined to the fixed part of said circular member at right angles with respect thereto, a pair of diametrically opposed rectangular output waveguide sections joined to the rotary part of the circular member at right angles with respect thereto and disposed so that the narrow dimension of the inner end of each is perpendicular to the plane of rotation of the output sections, said output sections being twisted intermediate their ends to an extent such that their output ends are disposed with the narrow dimension of each parallel to the plane of rotation of the output sections, a fixed sleeve enclosing the output ends of the output sections having a window therein in registry with the path of travel of said output ends and extending arcuately 180 degrees, the margins ofsaid fixed sleeve defining the ends of the window having dry load elements secured thereto to lessen the reflection from said margins, and a rotary sleeve enclosing the fixed sleeve and movable in unison with the rotary part of the circular member and having a pair of diametrically opposed rectangular external waveguide sections disposed in registry with the output ends of the output waveguide sections.

5. A radio frequency rotary switch, comprising a circular waveguidemember having a fixed part and a rotary part, a fixed rectangular input waveguide section joined to the fixed part of said circular member at right angles with respect thereto, there being a single step formed at the juncture of the outer wall of the inputsection and the fixed part of said circular member to match impedance-s at the transition point between the just mentioned parts and insure the creation of a circularly symmetrical mode in the circular member with a minimum creation of a non-symmetrical mode, a pair of diametrically opposed rectangular output waveguide sections joined to the circular waveguide member at right angles with respect thereto and disposed so that the narrow dimension of the inner end of each output section is perpendicular to the plane of rotation of the output section, said rotary part of the circular member extending beyond the inner ends of the output sections a distance equal to an even multiple of the quarter wave length of the circularly symmetrical mode in the circular member and an odd multiple of the quarter wave length of the linearly polarized mode in the circular member, said output sections being twisted intermediate their ends to an extent such that the output ends of the output sections are disposed with the narrow dimension of each parallel to the plane of rotation of the output section, a fixed sleeve enclosing the output ends of the output sections, and having a window therein in registry with the path of travel of said output ends and extending arcuately 180 degrees, the margins of said fixed sleeve defining the ends of the window and having dry load elements secured thereto to lessen the reflection from said margins, and a rotary sleeve enclosing the fixed sleeve and movable in unison with the rotary part of said circular member and having a pair of diametrically opposed rectangular external waveguide sections disposed in registry with the output ends of the output waveguide sections.

6. A radio frequency rotary switch comprising a fixed body member having a central circular opening, inner and outer bearings carried by the member concentric with the opening, a tubular member closed at its outer end and supported at its inner end upon the inner bearing in axial alignment with the opening and cooperating therewith to form a circular waveguide having rectangular outlet ports positioned with their short dimensions parallel to the axis of the member and spaced inwardly from the closed end thereof a distance equal to onehalf the wavelength of the dominant circularly symmetrical mode existing in the tubular member, internal rectangular waveguide sections joined to the tubular member and movable therewith in communication with the ports, said sections being twisted through approximately between the ports and the free ends of the sections, a fixed sleeve secured to the body member and extending past the ends of the internal waveguide sections, said sleeve having an opening past which the sec-' tions are movable successively, a rotary sleeve enclosing the fixed sleeve and provided with rectangular ports movable with the sleeve to register successively with the free ends of the internal waveguide sections through the open ing in the fixed sleeve, a rectangular input waveguide section secured to the fixed body member at right angles to and in communication with the opening therein, and rectangular output waveguide sections secured to the rotating sleeve over the ports at right angles to the sleeve and movable therewith.

(References on following page) McCl'ain Aug. 9, 1-955 FOREIGN PATENTS Great Britain Sept. 5, 1946 OTHER REFERENCES ".Rlg eirll, Microwave Transmission Circuits, vol. 9, Radiation Laboratory Series Published 1948, pp. 385 and 

